Neopentyl glycol (hereinafter as "NPG") is an important starting material for the preparation of various useful products such as synthetic resins, lubricants, surface coatings and plastics. NPG has commonly been produced by effecting an aldol condensation of isobutyraldehyde and formaldehyde, followed by the hydrogenation of the condensation product, hydroxypivaldehyde, such as those described in U.S. Pat. No. 2,400,724, U.S. Pat. No. 2,865,819 and U.S. Pat. No. 3,939,216. The type of aldol catalyst used with condensation reaction have been a base catalyst, such as alkali metal-containing catalyst, alkaline earth metal-containing catalyst and tertiary amines; the type of catalyst used with hydrogenation have been a heterogeneous catalyst, such as copper/chromium oxide, Pt-Ru-W and Raney nickel. The hydrogenation of the condensation product, hydroxypivaldehyde, has commonly been carried out by the gas sparged reactor, such as those described in U.S. Pat. No. 4,855,515. However, owing to the low efficiency of gas-liquid contact in the gas sparged reactor, low yield of NPG is obtained, unless it is necessary to conduct the hydrogenation under high pressures. These caused constraints on the process and equipment to be used and considerable problems, in particular in industry plants, where one must ensure high standards of safety and reliability, and high yield of NPG.
It is thus desirable to have a method which have high efficiency of gas-liquid contact for high yield of NPG, and without the need to conduct the reaction at high pressures.